1. Field of the Invention
The invention relates to a dual converter, suitable for a dual filter, of the kind that can be used in particular in television receiver sets as a single channel filter, instead of the two channel filters previously used.
2. Description of the Related Art
In TV sets, the prior art has conventionally used TV channel filters which, together with the high-frequency signal of a tunable oscillator, allow the TV viewer to make a selection of a desired channel. It has been known for decades to use TV filters constructed in accordance with surface acoustic wave technology.
The TV signals to be received on the channels assigned to the various TV stations have certain standardized characteristics. However, the standards are not uniform. For instance, even within Europe there are different standards, for example because of the various channel bandwidths in the different countries, such as in Germany and in France. A standard-specified different on-state performance of the channel filters for different standards is also provided.
For double-standard receivers in the prior art, for instance, two different surface acoustic wave filters are used as the channel filters, one for one standard and the other for the other standard. It is known for two such different channel filters to be disposed side by side on a substrate chip. However, nearly as much substrate material is needed for this as for two individual, separate filters together. Combining two channel filters for different standards on one substrate body of approximately twice the size (as compared to the single filter) serves essentially to simplify the mounting of the filter and the like.